Speed is a scalar and velocity is a vector.A scalar only has magnitude while a vector has magnitude and direction.

Example: If you are traveling north at 65 miles an hour your speed is 65 miles an hour, your velocity is 65 miles an hour north.It gets a little more complicated. Speed = distance (a scalar)/time Velocity = Displacement (vector)/time

Example: If you run 5 miles in an hour left and then 5 miles in a hour right your speed is 10 miles/2 hours = 5 miles an hour. However, since you end up in the same exact location as where you started your displacement is zero making your velocity zero as well. Think of it this way; since velocity is a vector it requires a direction if i ended up exactly where I started I have no direction, thus velocity must be zero.

One more example to clarify: If you ran 6 miles right and 4 miles left in 2 hours, your speed will be 5 miles an hour (10/2=5) your velocity would be 1 mile an hour to the right, since displacement is 2 miles to the right (6 to right - 4 to left = 2 to right) and the time is 2 hours displacement/time = velocity; 2 to the right/2 = 1 mile to the right per hour.

A man standing on a bus remains still when the bus is at rest. When the bus moves forward and then slows down the man continues moving forward at the original speed. This is an example of the effect of inertia.